The digital viewer trick is great, but you still need the paper schematic for some FAA paperwork. I keep a marked-up set in the hangar just for that.

Demand a refund, that's just lazy.

Oh man, that's the worst feeling. I get it though, buying a big tool for that one special job. It's like when Leo bought that cordless grinder for a single project and it's been on the shelf ever since. Sometimes the right tool saves the day, but then it just becomes this expensive thing you have to store. If it saved your back on that draft horse, maybe that alone was worth it, even if it doesn't come out for every client.